My son is about this age, and also stop taking the bottle since he is 16 months old. Since he has refused most milk products, and his growth chart has shown a curve. We also found out he has an anemic tendency, and shows some bags under his eyes. In addition he has had several bowel movements a day, that in my opinion are larger and more numerous than most toddler (I will not go into lengths here about all the full diaper disaster we have been having since March...). So after reaching what I felt was a dead point with his ped - he believed that there was not really something abnormal in all these signs or acted like if it was not worrisome - I ended up getting a aptmt with a dietetician. It was really helpful. I would suggest you do that. She was able to suggest some changes (more fibers, more meat which I was feeding my son but in unsufficient quantities), and ideas on how to reintroduce diairies in other forms. She also, after a second apointment, prescribed a supplement formula, some kind a vanilla flavored drink, that my son likes in small quantities. I am hoping that over the long run he will take more and more.
It is my suggestion..